The US Food and Drug Administration has given full approval to the Pfizer vaccine for Covid-19. The vaccine and others have been in use for months under emergency use authorisation.
The decision is likely to trigger a wave of formal vaccine requirements from government departments, businesses, schools and other bodies.
Many observers hope formal approval will spur an increase in vaccine take-up among sections of the population, particularly in Republican-led states, so far resistant to government advice.
More than 200m Pfizer doses already have been administered in the US since emergency use began in December, and hundreds of millions more worldwide.